scholarly journals Modelling of primary aerosols in the chemical transport model MOCAGE: development and evaluation of aerosol physical parameterizations

2015 ◽  
Vol 8 (2) ◽  
pp. 381-408 ◽  
Author(s):  
B. Sič ◽  
L. El Amraoui ◽  
V. Marécal ◽  
B. Josse ◽  
J. Arteta ◽  
...  
Keyword(s):  
Wet Deposition ◽  
Transport Model ◽  
Continuous Process ◽  
Volcanic Eruptions ◽  
Chemical Transport ◽  
Sea Salt ◽  
Chemical Transport Model ◽  
Precipitation Regime ◽  
Desert Dust ◽  
Model Average

Abstract. This paper deals with recent improvements to the global chemical transport model of Météo-France MOCAGE (Modèle de Chimie Atmosphérique à Grande Echelle) that consists of updates to different aerosol parameterizations. MOCAGE only contains primary aerosol species: desert dust, sea salt, black carbon, organic carbon, and also volcanic ash in the case of large volcanic eruptions. We introduced important changes to the aerosol parameterization concerning emissions, wet deposition and sedimentation. For the emissions, size distribution and wind calculations are modified for desert dust aerosols, and a surface sea temperature dependant source function is introduced for sea salt aerosols. Wet deposition is modified toward a more physically realistic representation by introducing re-evaporation of falling rain and snowfall scavenging and by changing the in-cloud scavenging scheme along with calculations of precipitation cloud cover and rain properties. The sedimentation scheme update includes changes regarding the stability and viscosity calculations. Independent data from satellites (MODIS, SEVIRI), the ground (AERONET, EMEP), and a model inter-comparison project (AeroCom) are compared with MOCAGE simulations and show that the introduced changes brought a significant improvement on aerosol representation, properties and global distribution. Emitted quantities of desert dust and sea salt, as well their lifetimes, moved closer towards values of AeroCom estimates and the multi-model average. When comparing the model simulations with MODIS aerosol optical depth (AOD) observations over the oceans, the updated model configuration shows a decrease in the modified normalized mean bias (MNMB; from 0.42 to 0.10) and a better correlation (from 0.06 to 0.32) in terms of the geographical distribution and the temporal variability. The updates corrected a strong positive MNMB in the sea salt representation at high latitudes (from 0.65 to 0.16), and a negative MNMB in the desert dust representation in the African dust outflow region (from −1.01 to −0.22). The updates in sedimentation produced a modest difference; the MNMB with MODIS data from 0.10 in the updated configuration went to 0.11 in the updated configuration only without the sedimentation updates. Yet, the updates in the emissions and the wet deposition made a stronger impact on the results; the MNMB was 0.27 and 0.21 in updated configurations only without emission, and only without wet deposition updates, respectively. Also, the lifetime, the extent, and the strength of the episodic aerosol events are better reproduced in the updated configuration. The wet deposition processes and the differences between the various configurations that were tested greatly influence the representation of the episodic events. However, wet deposition is not a continuous process; it has a local and episodic signature and its representation depends strongly on the precipitation regime in the model.

scholarly journals Modelling of primary aerosols in the chemical transport model MOCAGE: development and evaluation of aerosol physical parameterizations

2014 ◽  
Vol 7 (2) ◽  
pp. 2745-2796 ◽  
Author(s):  
B. Sič ◽  
L. El Amraoui ◽  
V. Marécal ◽  
B. Josse ◽  
J. Arteta ◽  
...  
Keyword(s):  
Wet Deposition ◽  
Transport Model ◽  
Continuous Process ◽  
Chemical Transport ◽  
Sea Salt ◽  
Chemical Transport Model ◽  
Precipitation Regime ◽  
Sea Temperature ◽  
Desert Dust ◽  
Model Average

Abstract. This paper deals with recent improvements to the chemical transport model of Météo-France MOCAGE that consists of updates to different aerosol parameterizations. MOCAGE only contains primary aerosol species. We introduced important changes to the aerosol parameterization concerning emissions, wet deposition and sedimentation. For the emissions, size distribution and wind calculations are modified for desert dust aerosols, and a surface sea temperature dependant source function is introduced for sea salt aerosols. Wet deposition is modified toward a more physically realistic representation by introducing re-evaporation of falling rain and snowfall scavenging, and by changing in-cloud scavenging scheme along with calculations of precipitation cloud cover and rain properties. The sedimentation scheme update includes changes regarding the stability and viscosity calculations. Independent data from satellites (MODIS, SEVIRI), the ground (AERONET), and a model inter-comparison project (AeroCom) is compared with MOCAGE simulations and showed that the introduced changes brought a significant improvement on aerosol representation, properties and global distribution. Emitted quantities of desert dust and sea salt, as well their lifetimes, moved closer towards values of AeroCom estimates and the multi-model average. When comparing the model simulations with MODIS aerosol optical depth (AOD) observations over the oceans, the updated model configuration shows a decrease in the bias (from 0.032 to 0.002) and a better correlation (from 0.062 to 0.322) in terms of the geographical distribution and the temporal variability. The updates corrected a strong positive bias in the sea salt representation at high latitudes (from 0.153 to 0.026), and a negative bias in the desert dust representation in the African dust outflow region (from −0.179 to −0.051). The updates in sedimentation produced a modest difference; the bias with MODIS data from 0.002 in the updated configuration went to 0.003 in the updated configuration only without the sedimentation updates. Yet, the updates in the emissions and the wet deposition made a stronger impact on the results; the bias was 0.041 and 0.032 in updated configurations only without emission, and wet deposition updates, respectively. Also, the lifetime, the extent, and the strength of the episodic aerosol events are better reproduced in the updated configuration. The wet deposition processes and the differences between the various configurations that were tested greatly influence the representation of the episodic events. However, wet deposition is not a continuous process; it has a local and episodic signature and its representation depends strongly on the precipitation regime in the model.

scholarly journals Global observations of tropospheric BrO columns using GOME-2 satellite data

2010 ◽  
Vol 10 (11) ◽  
pp. 28635-28685 ◽  
Author(s):  
N. Theys ◽  
M. Van Roozendael ◽  
F. Hendrick ◽  
X. Yang ◽  
I. De Smedt ◽  
...  
Keyword(s):  
Quantitative Study ◽  
Satellite Data ◽  
Transport Model ◽  
Chemical Transport ◽  
Sea Salt ◽  
Polar Regions ◽  
Blowing Snow ◽  
Chemical Transport Model ◽  
Sea Salt Aerosols ◽  
Good Level

Abstract. Measurements from the GOME-2 satellite instrument have been analyzed for tropospheric BrO using a residual technique that combines measured BrO columns and estimates of the stratospheric BrO content from a climatological approach driven by O3 and NO2 observations. Comparisons between the GOME-2 results and BrO vertical columns derived from correlative ground-based and SCIAMACHY nadir observations, present a good level of consistency. We show that the adopted technique enables separation of stratospheric and tropospheric fractions of the measured total BrO columns and allows quantitative study of the BrO plumes in polar regions. While some satellite observed plumes of enhanced BrO can be explained by stratospheric descending air, we show that most BrO hotspots are of tropospheric origin, although they are often associated to regions with low tropopause heights as well. Elaborating on simulations using the $p$-TOMCAT tropospheric chemical transport model, this result is found to be consistent with the mechanism of bromine release through sea salt aerosols production during blowing snow events. Outside polar regions, evidence is provided for a global tropospheric BrO background with column of 1–3×1013 molec/cm2, consistent with previous estimates.

scholarly journals Development of an aerosol chemical transport model RAQM2 and predictions of Northeast Asian aerosol mass, size, chemistry, and mixing type

2012 ◽  
Vol 12 (5) ◽  
pp. 13405-13456 ◽  
Author(s):  
M. Kajino ◽  
Y. Inomata ◽  
K. Sato ◽  
H. Ueda ◽  
Z. Han ◽  
...  
Keyword(s):  
Air Quality ◽  
Transport Model ◽  
Regional Scale ◽  
Chemical Transport ◽  
Sea Salt ◽  
Chemical Components ◽  
Air Quality Model ◽  
Chemical Transport Model ◽  
Wide Range ◽  
Northeast Asian

Abstract. A new aerosol chemical transport model, Regional Air Quality Model 2 (RAQM2), was developed to simulate Asian air quality. We implemented a simple version of a modal-moment aerosol dynamics model (MADMS) and achieved a completely dynamic (non-equilibrium) solution of a gas-to-particle mass transfer over a wide range of aerosol diameters from 1 nm to super μm. To consider a variety of atmospheric aerosol properties, a category approach was utilized, in which the aerosols were distributed into 4 categories: Aitken mode (ATK), soot-free accumulation mode (ACM), soot aggregates (AGR), and coarse mode (COR). Condensation, evaporation, and Brownian coagulations for each category were solved dynamically. A regional-scale simulation (Δ x = 60 km) was performed for the entire year of 2006 covering the Northeast Asian region. Statistical analyses showed that the model reproduced the regional-scale transport and transformation of the major inorganic anthropogenic and natural air constituents within factors of 2 to 5. The modeled PM1/bulk ratios of the chemical components were consistent with the observations, indicating that the simulations of aerosol mixing types were successful. Non-sea salt SO42- mixed with ATK + ACM was the largest at Hedo in summer, whereas it mixed with AGR was substantial in cold seasons. Ninety-eight percent of the modeled NO3- was mixed with sea salt at Hedo, whereas 53.7% of the NO3- was mixed with sea salt at Gosan, located upwind toward the Asian continent. The condensation of HNO3 onto sea salt particles during transport over the ocean makes the difference in the NO3- mixing type at the two sites. Because the aerosol mixing type alters optical properties and cloud condensation nuclei activity, its accurate prediction and evaluation are indispensable for aerosol-cloud-radiation interaction studies.

scholarly journals Development of the RAQM2 aerosol chemical transport model and predictions of the Northeast Asian aerosol mass, size, chemistry, and mixing type

2012 ◽  
Vol 12 (24) ◽  
pp. 11833-11856 ◽  
Author(s):  
M. Kajino ◽  
Y. Inomata ◽  
K. Sato ◽  
H. Ueda ◽  
Z. Han ◽  
...  
Keyword(s):  
Air Quality ◽  
Transport Model ◽  
Regional Scale ◽  
Chemical Transport ◽  
Sea Salt ◽  
Aerosol Size Distribution ◽  
Chemical Components ◽  
Chemical Transport Model ◽  
Wide Range ◽  
Northeast Asian

Abstract. A new aerosol chemical transport model, the Regional Air Quality Model 2 (RAQM2), was developed to simulate the Asian air quality. We implemented a simple version of a triple-moment modal aerosol dynamics model (MADMS) and achieved a completely dynamic (non-equilibrium) solution of a gas-to-particle mass transfer over a wide range of aerosol diameters from 1 nm to super-μm. To consider a variety of atmospheric aerosol properties, a category approach was utilized in which the aerosols were distributed into four categories: particles in the Aitken mode (ATK), soot-free particles in the accumulation mode (ACM), soot aggregates (AGR), and particles in the coarse mode (COR). The aerosol size distribution in each category is characterized by a single mode. The condensation, evaporation, and Brownian coagulations for each mode were solved dynamically. A regional-scale simulation (Δx = 60 km) was performed for the entire year of 2006 covering the Northeast Asian region. The modeled PM1/bulk ratios of the chemical components were consistent with observations, indicating that the simulated aerosol mixing types were consistent with those in nature. The non–sea-salt SO42− mixed with ATK + ACM was the largest at Hedo in summer, whereas the SOSO42− was substantially mixed with AGR in the cold seasons. Ninety-eight percent of the modeled NO3− was mixed with sea salt at Hedo, whereas 53.7% of the NO3− was mixed with sea salt at Gosan, which is located upwind toward the Asian continent. The condensation of HNO3 onto sea salt particles during transport over the ocean accounts for the difference in the NO3− mixing type at the two sites. Because the aerosol mixing type alters the optical properties and cloud condensation nuclei activity, its accurate prediction and evaluation are indispensable for aerosol-cloud-radiation interaction studies.

scholarly journals Seasonal variation of fine and coarse-mode nitrates and related aerosols over East Asia: Synergetic observations and chemical transport model analysis

2017 ◽  
Author(s):  
Itsushi Uno ◽  
Kazuo Osada ◽  
Keiya Yumimoto ◽  
Zhe Wang ◽  
Syuichi Itahashi ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Seasonal Changes ◽  
Transport Model ◽  
Chemical Transport ◽  
Sea Salt ◽  
Large Contribution ◽  
Acid Uptake ◽  
Chemical Transport Model ◽  
Coarse Mode ◽  
Microphysical Processes

Abstract. We analyzed long-term fine- and coarse-mode nitrate and related aerosols (SO42−, NO3−, NH4+, Na+, Ca2+) synergetic observations at Fukuoka (33.52° N, 130.47° E) from August 2014 to October 2015. A Goddard Earth Observing System chemical transport model (GEOS-Chem) including dust and sea-salt acid uptake processes was used to assess the observed seasonal variation, and the impact of long-range transport (LRT) from the Asian continent. For fine aerosols (fSO42−, fNO3−, and fNH4+), numerical results explained the seasonal changes, and a sensitivity analysis excluding Japanese domestic emissions clarified the LRT fraction at Fukuoka (85 % for fSO42−, 47 % for fNO3−, 73 % for fNH4+). Observational data for HNO3, fNO3−, and coarse NO3− (cNO3−) confirmed that cNO3− made up the largest proportion of total nitrate (defined as the sum of fNO3−, cNO3− and HNO3), constituting 40–55 % of total nitrate during the winter, while HNO3− gas constituted approximately 40 % of total nitrate in summer, and fNO3 peaked during the winter. A numerical model reproduced the seasonal variations in fNO3−. For cNO3−, large-scale dust-nitrate outflow from China to Fukuoka was confirmed during all dust events that occurred between January and June. Modeled cNO3− was in good agreement with observations between July and November (mainly coming from sea salt-NO3−). However during the winter, the model underestimated cNO3− levels compared to the observed levels. The reason for this underestimation was examined statistically using multiple regression analysis (MRA). We used cNa+, nss-cCa2+, and cNH4+ as independent variables to describe the observed cNO3− levels; these variables were considered representative of sea salt-cNO3−, dust-cNO3−, and cNO3− accompanied by cNH4+ (cNH4+ term), respectively. The MRA results explained the observed seasonal changes in dust-cNO3− and indicated that the dust-acid uptake scheme reproduced the observed dust-nitrate levels even in winter. The annual average contributions of each component were 43 % (sea salt-cNO3−), 19 % (dust cNO3−), and 38 % (cNH4+ term). The MRA dust-cNO3− component had a high value during the dust season, and the sea salt component made a large contribution throughout the year. During the winter, cNH4+ term made a large contribution. The model did not include aerosol microphysical processes (such as condensation and coagulation between the fine anthropogenic aerosols NO3− and SO42− and coarse particles), and our results suggest that inclusion of aerosol microphysical processes is critical when studying observed cNO3− formation, especially in winter.

scholarly journals Global observations of tropospheric BrO columns using GOME-2 satellite data

2011 ◽  
Vol 11 (4) ◽  
pp. 1791-1811 ◽  
Author(s):  
N. Theys ◽  
M. Van Roozendael ◽  
F. Hendrick ◽  
X. Yang ◽  
I. De Smedt ◽  
...  
Keyword(s):  
Quantitative Study ◽  
Satellite Data ◽  
Transport Model ◽  
Chemical Transport ◽  
Sea Salt ◽  
Polar Regions ◽  
Blowing Snow ◽  
Chemical Transport Model ◽  
Sea Salt Aerosols ◽  
Good Level

Abstract. Measurements from the GOME-2 satellite instrument have been analyzed for tropospheric BrO using a residual technique that combines measured BrO columns and estimates of the stratospheric BrO content from a climatological approach driven by O3 and NO2 observations. Comparisons between the GOME-2 results and BrO vertical columns derived from correlative ground-based and SCIAMACHY nadir observations, present a good level of consistency. We show that the adopted technique enables separation of stratospheric and tropospheric fractions of the measured total BrO columns and allows quantitative study of the BrO plumes in polar regions. While some satellite observed plumes of enhanced BrO can be explained by stratospheric descending air, we show that most BrO hotspots are of tropospheric origin, although they are often associated to regions with low tropopause heights as well. Elaborating on simulations using the p-TOMCAT tropospheric chemical transport model, this result is found to be consistent with the mechanism of bromine release through sea salt aerosols production during blowing snow events. No definitive conclusion can be drawn however on the importance of blowing snow sources in comparison to other bromine release mechanisms. Outside polar regions, evidence is provided for a global tropospheric BrO background with column of 1–3 × 1013 molec cm−2, consistent with previous estimates.

scholarly journals Seasonal variation of fine- and coarse-mode nitrates and related aerosols over East Asia: synergetic observations and chemical transport model analysis

2017 ◽  
Vol 17 (23) ◽  
pp. 14181-14197 ◽  
Author(s):  
Itsushi Uno ◽  
Kazuo Osada ◽  
Keiya Yumimoto ◽  
Zhe Wang ◽  
Syuichi Itahashi ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Seasonal Changes ◽  
Transport Model ◽  
Chemical Transport ◽  
Sea Salt ◽  
Large Contribution ◽  
Acid Uptake ◽  
Chemical Transport Model ◽  
Coarse Mode ◽  
Microphysical Processes

Abstract. We analyzed long-term fine- and coarse-mode synergetic observations of nitrate and related aerosols (SO42−, NO3−, NH4+, Na+, Ca2+) at Fukuoka (33.52° N, 130.47° E) from August 2014 to October 2015. A Goddard Earth Observing System chemical transport model (GEOS-Chem) including dust and sea salt acid uptake processes was used to assess the observed seasonal variation and the impact of long-range transport (LRT) from the Asian continent. For fine aerosols (fSO42−, fNO3−, and fNH4+), numerical results explained the seasonal changes, and a sensitivity analysis excluding Japanese domestic emissions clarified the LRT fraction at Fukuoka (85 % for fSO42−, 47 % for fNO3−, 73 % for fNH4+). Observational data confirmed that coarse NO3− (cNO3−) made up the largest proportion (i.e., 40–55 %) of the total nitrate (defined as the sum of fNO3−, cNO3−, and HNO3) during the winter, while HNO3 gas constituted approximately 40 % of the total nitrate in summer and fNO3− peaked during the winter. Large-scale dust–nitrate (mainly cNO3−) outflow from China to Fukuoka was confirmed during all dust events that occurred between January and June. The modeled cNO3− was in good agreement with observations between July and November (mainly coming from sea salt NO3−). During the winter, however, the model underestimated cNO3− levels compared to the observed levels. The reason for this underestimation was examined statistically using multiple regression analysis (MRA). We used cNa+, nss-cCa2+, and cNH4+ as independent variables to describe the observed cNO3− levels; these variables were considered representative of sea salt cNO3−, dust cNO3−, and cNO3− accompanied by cNH4+), respectively. The MRA results explained the observed seasonal changes in dust cNO3− and indicated that the dust–acid uptake scheme reproduced the observed dust–nitrate levels even in winter. The annual average contributions of each component were 43 % (sea salt cNO3−), 19 % (dust cNO3−), and 38 % (cNH4+ term). The MRA dust–cNO3− component had a high value during the dust season, and the sea salt component made a large contribution throughout the year. During the winter, cNH4+ term made a large contribution. The model did not include aerosol microphysical processes (such as condensation and coagulation between the fine anthropogenic aerosols NO3− and SO42− and coarse particles), and our results suggest that inclusion of aerosol microphysical processes is critical when studying observed cNO3− formation, especially in winter.

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